Gray whales are among the largest and most charismatic animals in the ocean, but they may also be unwittingly ingesting millions of tiny pieces of human-made pollution every day.
A new study by Oregon State University researchers has estimated that gray whales feeding off the Oregon Coast consume up to 21 million microparticles per day, a finding informed in part by poop from the whales.
Microparticle pollution: a growing threat
.GUILLERMO ARIAS/AFP via Getty Images
Microparticle pollution includes microplastics and other human-sourced materials, such as fibers from clothing, that are less than 5 millimeters in size, as per Phys.org.
These particles are increasing exponentially in the environment and are predicted to continue doing so in the coming decades, according to the researchers.
Microparticle pollution poses a threat to the health of gray whales and other marine organisms, as they can accumulate in their tissues and organs, cause physical damage, interfere with digestion, and transport harmful chemicals and pathogens.
Microparticle pollution may also affect the quality and availability of the prey that gray whales rely on.
Dr. Susanne Brander, an associate professor and ecotoxicologist at Oregon State and co-author of the study, said: "This issue is gaining momentum globally and some states, such as California, have taken important steps. But more action needs to be taken, including here in Oregon, because this problem is not going away anytime soon."
Poop and Prey: how researchers made the Estimate
The study focused on a subgroup of about 230 gray whales known as the Pacific Coast Feeding Group.
They spend winters in Baja California, Mexico, and migrate north to forage in coastal habitats from northern California to southern British Columbia from June through November.
Since 2015, Dr. Leigh Torres, an associate professor at Oregon State and an author of the paper, and her team have used drones and other tools to study the health and behavior of this subgroup of gray whales off the Oregon Coast.
As part of this work, they collect poop samples from the whales.
For the new study, the researchers collected zooplankton, which are an important food supply for gray whales, and commercial and recreational fish.
They analyzed the microparticle loads in 26 zooplankton samples collected from whale feeding areas and found microparticles in all of them.
They also found microparticles in all 18 fish samples collected from local markets.
Using these data and information on gray whale feeding behavior and energy requirements, the researchers estimated that gray whales consume between 3.9 million and 21 million microparticles per day during their foraging season off the Oregon Coast.
Gray whales are unique among baleen whales in their ability to feed on both planktonic and benthic prey, as per NOAA.
Planktonic prey are microscopic organisms that float in the water column, while benthic prey are animals that live on or near the seafloor.
Gray whales feed on planktonic prey by swimming slowly with their mouths open and filtering their food through their baleen plates.
They feed on benthic prey by turning on their sides and scooping up sediments from the seafloor. They then expel the water and mud through their baleen plates, retaining only their food items.
Gray whales can easily switch from feeding planktonically to benthically depending on their location and behavior.
They tend to feed benthically when they are in shallow coastal waters where they can find abundant prey, such as amphipods (small crustaceans), polychaetes (marine worms), or mysids (shrimp-like animals).
They tend to feed planktonically when they are in deeper offshore waters where they can find swarms of krill (small crustaceans) or copepods (tiny crustaceans), as per American Oceans
Gray whale feeding behavior is influenced by several factors such as seasonality, habitat quality, prey availability, competition, predation risk, and environmental conditions.
They may also modify their feeding behavior in response to human activities such as noise or vessel traffic.
Its feeding behavior is a remarkable adaptation that allows it o exploit a variety of food resources in different habitats.
However, it also exposes the creature to a higher risk of ingesting microparticle pollution, which may have negative consequences for their health and survival.
